If it's more Columbine then it wouldn't be Jihadist. And as far as can be determined the "outside assistance" was an internet connection.
He was talking from a legal perspective. Nobody seriously doubts that this wasn't a Jihadist inspired attack, apart from perhaps yourself. He says "Two kids who radicalized between themselves in a closed circle go out and commit murder. I would charge these guys as murders". That is why he was referring to Columbine.